Porto Alegre was founded in 1769 by Manuel Jorge Gomes de Sepúlveda, who used the pseudonym José Marcelino de Figueiredo to hide his identity; but the official date is 1772 with the act signed by immigrants from the Azores, Portugal. The vast majority of the population is of European descent.

The city lies on the eastern bank of the Rio Guaiba (Guaiba Lake), where five rivers converge to form the Lagoa dos Patos (Lagoon of the Ducks), a giant freshwater lagoon navigable by even the largest of ships. This five-river junction has become an important alluvial port as well as a chief industrial and commercial center of Brazil.